Chernobyl is far from the only place on the planet that human beings have rendered uninhabitable. War can leave formerly civilized lands open for wildlife. Tigers rebounded in Southeast Asia during the Vietnam War because combat drove out the farmers that killed them to protect their families and livestock. The kouprey, a wild cow and one of the rarest animals on the planet, may have also benefited. Thought to be extinct, kouprey were spotted in the Vietnamese highlands in 1988.

Preparation for war also excludes people from swaths of territory surrounding military bases and weapons production facilities. The Savannah River Site, which produced plutonium and tritium for nuclear weapons, carved 350 square miles out of South Carolina that have been virtually undisturbed for decades. In 2001, federal lands around the Rocky Flats nuclear facility in Colorado were officially declared a national wildlife refuge.

Buffer zones between warring tribes or countries can also create no-man’s-lands. Borderlands between Native American tribes in the American West may have preserved big game such as buffalo and elk from the extinction that other North American megafauna suffered after the arrival of humans 13,000 years ago. In the last century, the demilitarized zone between North and South Korea became a patch of

paradise. Like the flaming sword that God installed east of Eden to prevent man from reentering after the expulsion of Adam and Eve, land mines and machine guns kept people out of the DMZ, making it welcoming for wildlife.

Science fiction writer Bruce Sterling coined the term “involuntary parks” to describe places that have been reclaimed by nature and reverted to savagery because of war, pollution, or other disasters. Involuntary parks do not, as Sterling puts it, represent untouched nature, but “vengeful nature”—natural processes reasserting themselves in areas of political and technological collapse.

Few terms have struck me as more appropriate to describe the Zone of Alienation around Chernobyl. Even the name, bestowed by bureaucracy, conjures the zone’s rejection, its indifference to humans.

While civilization with one hand destroys habitats and leads to the extinction of species, it can also do the opposite with the other. University of Arizona paleoecologist Paul Martin, for example, advocates the creation of nature preserves that would re-create the pre-Indian, Ice Age world with African or Asian elephants standing in for the extinct North American elephant species. Bruce Sterling goes further and, his tongue only partly in cheek, suggests that DNA from frozen mammoths in Siberia be used to resurrect mammoths—if and when that becomes technically feasible.

Sterling maintains that civilization has done so much damage to the environment, including climate change, that we can’t rely on nature to reassert itself without some ambitious interventions. Extinct species such as mammoth will not resurrect no matter how many voluntary or involuntary parks are created. While resurrecting extinct species, even if it becomes possible, poses problems of its own—woolly mammoth would probably find it a tad warm if global warming proceeds apace—Chernobyl offers surprising examples of species that were brought to the brink of extinction and are now thriving in the wild.

It was a snowy, windy, and freezing December day at the close of 2003 when I once again found myself off-roading in the Chornobyl fire department’s UAZ jeep. It was actually the last place I wanted to be at that particular time. But two scientists that I had been eager to meet

for months had come to the zone for a week-long visit. Since tight funding allowed them to visit only once a year, I couldn’t pass up the opportunity.

Sasha Berovsky, the Chernobyl fire chief, was in front with the driver, Mykola, while I sat squeezed between Tatiana Zharkikh and Natalia Yasynetska in the back. The two scientists were from Askania Nova, a nature preserve in southern Ukraine, which is one of the few places one can see what the natural steppe looked like before cultivation and industrialization destroyed it. It is also the world’s largest breeding facility for endangered Przewalski’s horses, a stocky species of wild horse that survived only in zoos until recently.

“We breed some Ukrainian Riding Horses, too,” said Tatiana, a thirtyish biologist who has worked at Askania Nova since 1992. “It’s a unique breed. Have you heard of it?”

Actually I had. The Ukrainian Riding Horse was one of a number of breeds developed in the Soviet Union whose existence was virtually unknown in the West until the USSR collapsed. But I wasn’t sure if I knew what exactly was so unique about the breed, so I asked Tatiana.

“It’s the combination of their good athletic qualities with their endurance,” Tatiana responded.

“And their ability to live in poor conditions,” added Natalia, a petite geneticist who has been working with rare animals, including the Przewalskis, at Askania Nova since 1975.

In Soviet times, the poor conditions were due largely to the shortage-ridden economy. In Ukraine the problem was money—especially in the early years of independence when the state-run economy crumbled and a market had not yet formed to replace it. Thousands of horses were slaughtered because there was simply no way to feed them. The best were exported for pennies to Europe.

The scientists had come to the zone to check on some Przewalski’s horses that were released into the wild in a controversial experiment several years earlier. I had met with some of the program’s opponents in Kiev and was curious about how Tatiana and Natalia would react to their critics.

“One former zone biologist told me that the real reason it was done was because Askania had too many of the horses for its facilities,” I said. “Since the horses are endangered, they can’t be killed, so you brought them here instead.”

“That’s not true,” Natalia insisted. “Ukraine has no more and no

less captive Przewalski’s horses than its facilities—in Askania Nova and in parks—can accommodate. All over the world, the problem with endangered and rare species bred in captivity is that there is no place to let them go free.”

This was logical. Lack of space and forage shortages were also problems for the bison in the Bialowiecza reserve, which is why some animals were brought to the Belarusian zone.

One of the main reasons for species extinction is habitat extinction. The European bison used to roam the continent in great herds in Roman times, but as their primordial forest habitat shrank, so did their numbers until the species was pushed into its last refuge in the Bialowiecza forest. This is why the bison are being reintroduced in the same place that was their last home. Unlike the American buffalo, which were plains creatures, the European bison is a woodlands species.

The habitat of Przewalski’s horses has also been shrinking steadily since the last Ice Age, when northern parts of Europe were covered by ice sheets and good portions of the rest were arid steppe. Artists of that ancient era painted caves in France, Italy, and Spain with more than 600 depictions of equines resembling Przewalski’s horses. But when the ice retreated, the steppes in much of Europe became forested. The exception was a wide strip of territory that extended from the Hungarian plain, through southern Ukraine and eastward into Eurasia, where wild horses were abundant into Neolithic times. Indeed, horses were first domesticated on the steppes between the Dnieper and Ural Rivers sometimes around 3500 B.C.E., though it is not clear if the horses were Przewalski’s or Tarpans. More similar in appearance to domestic horses than Przewalski’s, Tarpans were wild horses that lived in Ukraine and Eastern Europe until the last one died near Askania Nova in 1897.

Little was known in the West about the Przewalski’s before their “discovery” in Mongolia in 1878 by Colonel Nikolai Przewalski, a Russian explorer of Polish origin in the service of the czar. Of course, the Mongolians knew all about the horses, which they called takhi and hunted for food. But the discovery of a previously unknown species of wild horse, named in the explorer’s honor, sparked the interest of European zoos and animal collectors. First among them was Baron Friederich E. von Falz-Fein, a German-born landowner with an estate called Askania Nova in the steppes of what was then southern Russia

and is now southern Ukraine. He sponsored the first expedition to capture the horses.

Because adult horses proved too fast to capture, the expeditions focused on foals, but the first captives died when fed sheep’s milk. Later expeditions became more successful once the hunters realized that domestic mares could nurse the wild foals, and the first Przewalski’s foals were delivered to Askania Nova in 1899. Altogether, four expeditions caught 53 foals that survived and were sold to Askania Nova as well as other zoos and collectors. But although Askania Nova—which the Communists nationalized and turned into a state nature reserve—was successful in breeding the horses, producing 37 foals over 40 years, the horses generally did not breed well.

Many Przewalski’s were also killed during fighting in World War II. When it was over, only 31 horses were left in captivity. And those survivors became extremely important in the 1960s, when severe weather, expanding livestock pastures, and an increase in horse hunting led to the Przewalski’s horses’ extinction in the wild. In 1960 there were only 59 Przewalski’s horses in the world.

With careful husbandry, however, the Przewalskis became a captive breeding success story. By the mid-1980s, there were more than 600 horses, enough to consider experimentally releasing some into the wild. As of 1999, there were more than 1,500. With 89 head in 2003, Askania Nova had the world’s largest collection. But although there were relatively plenty of horses worldwide, there were few suitable wild habitats for them.

“At Askania, we developed a release program if appropriate places could be found,” Natalia said. “After all, Ukraine, including Polissia, had been home to Tarpans in the past.”

“We thought to do it in the Crimean Mountains, where there are good pastures,” added Tatiana. “But the Crimean Tatars have been taking over the land there and using the pastures for domestic livestock.”

Deported en masse to Central Asia by Stalin in 1944, Crimean Tatars have been returning to their ancestral lands in what is now Ukraine since the waning days of the Soviet Union. But since their homes and lands were largely settled by ethnic Russians that Stalin sent to Crimea to replace the deportees, many Tatars have been taking whatever lands are left. Unfortunately, the Crimean Tatars suffer one of many Soviet-era injustices that can’t be easily remedied.

“Then, in Chernobyl, they came up with the idea of introducing different animals to the zone,” Natalia continued.

The program, called “Fauna,” was the brainstorm of some Chernobyl forestry officials concerned about “excess vegetation” creating fire hazards on the zone’s fallow lands. They suggested bringing in Przewalski’s horses, European bison, even beef cattle, that would eat the grass, trample the ground, and instinctively and cheaply perform other environmental management duties. The idea had a certain logic but for the fact that the zone had already become populated with plenty of wild animals. The program met with fierce opposition from many zone specialists in Ukraine. In Belarus, in contrast, there was little dissent over the bison program—perhaps because dissent in general was less tolerated in that country.

The Askania Nova scientists were cautious at first.

“But since we had been looking for an appropriate place to release small herds into the wild, we decided it was a good idea,” said Natalia. “After all, if this is a place where the horses can be free, why not try it as an experiment? There are places in the zone where the radioactivity is not very high.”

“Look!” Sasha interrupted when a lone red deer ran across our path.

“Make a note, Natalia,” said Tatiana, who then explained to me that they were also assessing the number and status of other ungulates in the zone.

Given the fact that all of these ungulates are radioactive, I asked if they had done any studies of radioactivity in the horses.

“We sent samples from a mare that died of natural causes to the Institute of Agricultural Radiology outside of Kiev, and all that they told us was that the radioactivity levels were within established norms,” said Tatiana.

That was surprising. Horses—like roe deer—eat grass, which is highly radioactive.

But at least the Askania Nova scientists got to test a specimen. As of 2004, Belarus scientists couldn’t directly measure the radionuclides in the zone’s bison and could only estimate it indirectly, by measuring radioactivity levels in their food and manure.

When I asked if the small world of Przewalski’s horses professionals criticized the idea of introducing the horses into a radioactive zone, Tatiana sighed before answering: “You can’t even imagine. But Askania

Nova isn’t pristine either. There are few parts of the Earth that aren’t damaged.”

“Then we saw the tremendous number of hoofed animals already living in the zone—red deer, elk, boars,” Natalia added, as the jeep bumped and jolted across the brush. “There was even a herd of feral domestic horses that were left behind after the evacuation, but they were taken away after the Przewalski’s program started to prevent cross-breeding.”

Though it is sometimes said that Przewalskis were the ancestors of domestic horses, genetic studies suggest that the two species diverged before horse domestication.

Przewalski’s horses have 66 chromosomes and domestic horses have 64, but the genetic difference between the two is evidently smaller than that between, say, domestic horses and donkeys. When horses and donkeys cross-breed, their offspring—mules—are sterile (with exceedingly rare exceptions). But Przewalskis bred with domestic horses produce fertile young.

“If all those animals were doing well, there was no reason why our horses wouldn’t either. After all, in Askania Nova we have to strictly limit the horses’ breeding—even that of the best specimens. There’s simply no space. But here they can be free and do what nature intended—reproduce. Then, after we brought the horses in and saw that the foals born in the zone survived the winter very well, we saw that the program was a success and we brought in another group of horses.”

Altogether, 31 horses—28 from Askania Nova plus 3 from a small zoo on a Kharkiv stud farm—were brought to the zone in 1998 and 1999. Ten of them died, mostly in transport. Although domestic horses can also panic in transport, semiwild Przewalski’s horses can literally die from the stress of being cut off from their herd, locked into a tight and dark crate, and driven in a truck for the 15 or so hours it takes to get from Askania to the zone. Young horses are especially vulnerable.

The 21 horses that survived were initially kept in a 100-hectare semireserve enclosed by a six-foot fence to adjust to the new climate. Polissia is colder and wetter than the steppe to which they had grown accustomed, and the horses needed time to figure out what was edible and what wasn’t, while getting supplemental feed rations from the Fauna program’s rangers. They ranged freely for months, using a former poultry farm’s barns for shelter and a small natural pond for water that they shared in the summer with wild ducks.

Not everything went according to plan. One December day an Askania Nova stallion named Volny, or “Free,” broke the barriers, herded some unattached mares, and took off. Since it was too soon to release the horses into the wild, the Fauna rangers herded them back into the enclosure and fixed the fence. But Volny, who fully lived up to his name, broke the fence again and freed his mares for good.

Another group of mares had formed a family group with Pioneer, a seven-year-old stallion from the Kharkiv stud farm. But another Askania Nova stallion named Vypad, whose name means “Attack,” also lived up to his name by beating Pioneer mercilessly and then stealing his mares. As if that wasn’t enough, Vypad broke the enclosures several days later to beat up Pioneer again, for no reason except he evidently didn’t like Przewalski’s stallions from Kharkiv. Vypad didn’t attack any Askania Nova stallions.

After that, poor Pioneer was terrified of Przewalski’s stallions and hid if they came anywhere near the enclosure. He ended up covering domestic mares, but the resulting hybrid foals were eventually sent to slaughterhouses.

“But aren’t you supposed to avoid hybridization in these introduction programs?” I asked the scientists after they told me the story. In fact, all the Przewalski’s alive today have a drop of domestic blood from a mare that served as a foster mother to foals transported from Mongolia. One aim of Przewalski’s breeding programs is to dilute that drop as much as possible.

Natalia hesitated and answered carefully: “Any program has those who plan and those who execute. And one of the people in the working group for some reason thought that he was the first person to try hybridization and was determined to do it, though we insisted that it was a bad idea.”

In the end, none of the Kharkiv stallions ended up with mares or in the wild. Kept in small groups in the stud farm’s zoo, they were practically domesticated and learned few of the social skills needed to do what stallions must in the wild. Askania Nova, in contrast, keeps the bachelor stallions in large herds of up to 30 head where they learn to fight—for food, for their place in the hierarchy, and eventually, if they are lucky, for mares. By the time they were brought to Chernobyl, the stallions were experienced adults.

They took to the wild with relish. The herds rarely returned to the

place of their semifree captivity even though it was within their range. Instead they seemed to be expanding their territory.

By December 2003, the wild population had grown to 65 head—two-thirds of them born in the zone—and divided into three groups. Two groups are family herds, called harems, of mares and their young offspring, usually (but not always) headed by a stallion. Volny led a smaller harem of five mares and their youngsters. But Vypad led the largest herd of eight breeding mares.

The remaining horses formed what is called a bachelor herd, which—as suggested by the name—contains stallions that have not yet managed to collect any mares. Like a gang of guys on the prowl, the bachelor herds are less stable than the harems, as stallions occasionally run off in search of mares and then return again to hang out with the boys. When they were first released, some bachelors were able to kidnap domestic mares kept at various zone services until the domestic horses were rounded up and removed. So, hunting farther and farther afield for mates, stallions have been sighted outside the zone, and their spoor has even been spotted in the Belarus part of the zone, which they probably reached by crossing the frozen Pripyat in winter.

The herds today are essentially on their own. The Fauna program and its funding were shut down in 2000, so the only people keeping track of the horses are the two Askania Nova scientists, whose tiny budget lets them visit the zone only once a year, and Sasha, the fireman, who keeps a regular watch and squires the scientists when they visit.

“He’s the top stallion!” said Tatiana. “Without him, we wouldn’t be able to do anything here. And he does it on pure enthusiasm!”

Blushing from the praise, Sasha laughed and then modestly changed the subject. “The horses have everything they need here. Not just food, but space—there’s no other place in Ukraine where they can have so much territory.”

“In Askania, there’s only enough pasture for about 90 head,” he added. “And here, the pasturage is….”

“Everywhere,” I said, wiping at the window to gaze at the fallow fields carpeted with thick piles of yellowed grasses, lightly frosted with snow. With freezing temperatures outside and five people inside, the jeep’s windows kept fogging up. It also smelled of exhaust and gasoline, from a canister behind the back seat.

“How about predators?” I asked. “Wolves?”

“They’re not afraid of wolves,” said Sasha. “Wolves are afraid of them.”

“Actually, the wolf problem or lack thereof depends largely on the herd stallions,” Tatiana said. “Their main job is to protect the herd, and especially vulnerable foals, from predators. Vypad and Volny haven’t lost a single foal.”

“But if they have no natural enemies in the zone, won’t they overpopulate?” I asked, recalling disastrous species introductions such as rabbits in Australia.

“No,” said Tatiana. “Because even though there’s enough pasturage for thousands of horses, their populations will be limited by the fact that Przewalski’s herds don’t like to be close neighbors with other herds. By our calculations, each Przewalski’s horse in a herd needs 20 hectares of territory a year. That’s far more pasture than the horse is able to eat.”

The remaining pasture was what each horse needed for its personal space. Added together, it was what each herd needed for its collective space. And each space had definite borders. The zone’s two family herds were separated by a six-mile border of no-horse-land that neither entered.

Once the Askania Nova scientists saw that the horses were doing well in the wild, they had hoped to bring in more horses to increase the genetic diversity.

“The international practice with introductions is to release the horses in family groups of a stallion and five mares,” said Tatiana as we drove around a small lake surrounded by picnic tables placed there by forest rangers. “But we now think its better to limit each stallion to two mares, while increasing the number of small herds so that more stallions can take part in reproduction.”

Unfortunately, the Fauna program died before they could test their ideas.

We were driving through Volny’s home range just west of Chernobyl. At 170 square kilometers, it was, according to Tatiana, the largest home range of any wild Przewalski’s herd in the world. The size is even more impressive when you have to trundle through it for many, many hours in a bouncing jeep to find the horses. We had been traveling for several

hours, with no sign of them. The occasional mounds of manure we spotted were cold and dusted with snow.

“In the early years after we released the horses, seeing manure meant you were about to see the horses,” said Natalia. “Now, their ranges have gotten so large that it doesn’t mean anything.”

Volny’s herd’s range was about half the size of Vypad’s. It also covered the most radioactive parts of the 10-kilometer zone. After kidnapping his mares in December 1999, Volny led his new harem to the buried village of Kopachi. Aside from being one of the most radioactive places in the 10-kilometer zone, Kopachi is also one of the busiest places outside the nuclear plant and the town of Chornobyl because the road between the two runs right through it. So, the following spring the herd moved to the area around the Red Forest and the highly contaminated western arrow of plutonium-embedded fuel particles that exploded from the reactor on April 26, 1986.

The colorful radiation maps depicted the plutonium contamination in the shape of a swallowtail butterfly—a rare species that is now common in the zone—with gradually fading wings extended from either side of the power plant. The deepest hues on the western wing, reflecting contamination levels between 400,000 and 1,000,000 becquerels per square kilometer, were right in Volny’s range.

Like plutonium, the uranium-235 and 238 in the fuel can also emit alpha particles. But because plutonium has a shorter half-life than either uranium isotope and because its alpha particle is much more powerful, plutonium-239 is hundreds of thousands of times more harmful per gram than uranium-238 and tens of thousands of times more harmful than uranium-235. These numbers don’t reflect biological damage. Plutonium is harmful only if it is ingested or inhaled. But horses that graze on a plutonium field are more likely to ingest or inhale the radionuclides than those that don’t.

It was sadly ironic that the stallion found safety from humans and their noisy vehicles in the most radioactive outdoor environment on the planet. Since Przewalski’s horses have survived only in captivity, it seemed to me that their human stewards bore them greater responsibility than, say, wild animals and I wondered whether it was right to deliberately release the horses into a radioactive zone when they have no way of knowing where it’s safe and where it isn’t.

Nevertheless, by releasing the horses into the zone, and breeding more horses to replace them at Askania Nova, there were 62 more

Przewalski’s horses on the planet than there would have been otherwise. In short, I was ambivalent about whether I thought it was a good idea.

Vypad, in any case, was more fortunate. No square kilometer in his range exceeded 4,000 becquerels of plutonium. In general, it is one of the zone’s least contaminated areas. Maybe that’s why the mare that died was within radiation norms. A boar shot in Vypad’s range registered less than 100 becquerels per kilogram of muscle—well below permissible limits—although animals in other parts of the zone can register thousands of becquerels.

Overlooking a field of experimental rye, containing several bounding roe deer and no horses, Sasha lamented: “Look at all this great grass. Why aren’t they here?”

Visibility was so poor because of the falling snow that binoculars were of little help. In the ghost village of Korohod, where our jeep got stuck in Chapter 4, Sasha climbed to the top of a fire tower for a better view while the rest of us got out to stretch our legs and breath some fresh air. It was windy outside and the snowflakes blew into my face like tiny pins.

Windy days after a stretch of dry weather are the worst times to be in the zone because the wind shears dust—and radionuclides—resuspending them into the air where they can be inhaled. It seemed counterintuitive to me, but large particles are more easily resuspended than small ones because they have a larger surface area for the wind shear to act on. Gravity quickly pulls back on particles that are larger than a few dozen micrometers, so even very high winds usually won’t raise them high enough to be inhaled. Instead, while wind carries smaller particles far afield, the larger ones just creep incrementally along the surface.

A tornado could carry more than a curie of radionuclides outside of the zone, but even less dramatic weather spreads contamination, just by blowing about fallen leaves, which contain a good part of the radionuclides taken up by trees. That’s why differences in radioactivity levels between the “dirtiest” and “cleanest” parts of the zone have been gradually growing smaller in the years since the disaster. Clean leaves blow into dirty sections, diluting the contamination, while radioactive leaves skip into clean areas, increasing it. The contamination is still quite patchy, however. Radionuclides in grass samples taken from the

same field can differ by a factor of two. The same is not true of trees, however, because their extensive root systems negate the patchiness.

Rain can also spread surface radioactivity, especially the first raindrops falling on very dry ground and raising tiny puffs of dust. But a lot of rain tends to keep radionuclides that are in the ground from wandering very far, even on very windy days. Wet soil particles are heavy and sticky, so the wind’s transport of radionuclides on rainy days is nearly zero. Snow cover also keeps them in their place, though the light snow falling that day had barely started to actually cover anything so it probably offered little protection to us.

While windy days usually raise radiation levels in the air, not all meteorological peaks come from stirring up radionuclides that are in the ground. Scientists were baffled when radiation levels in Europe surged at the end of May 1998. There is some evidence that the source was a Spanish steel mill smelting radioactive scrap metal. But the radionuclides may, in fact, have rained down from the stratosphere, where some radionuclides from atmospheric nuclear testing and Chernobyl ended up. Although it is generally aloof from the troposphere—where we live and where our weather happens—sudden changes in wind direction can cause the stratosphere to leak some of its contents towards Earth. That may be what happened in the anomalous May of 1998.

There have been other strange peaks as well. One that occurred in April 2002 may have been due to a radioactive release from the Sarcophagus or one of the facilities for processing nuclear waste.

After Sasha climbed down the fire tower bearing no good news, we climbed back into the jeep and he directed the driver over the zone’s labyrinthine firebreaks, trails, and fields with the confidence (astonishing to me) of knowing exactly where he was going in the wilderness. The going was rough at times, like violent turbulence with no seat belts. On several occasions my head nearly banged against the roof.

I wondered how much radioactivity we were kicking up in our wake. Any kind of mechanical work on contaminated territory can expose the more radionuclide-rich layers of soil beneath the surface and locally pick up dust that could get carried off a distance by the wind. That mechanical work could be accomplished by the jeep’s wheels, our shoes, or the hoofs of some galloping Przewalski’s horses.

Because Przewalski’s herds need such big spaces, the number of herds will be limited naturally by the zone’s size. Tatiana calculated that its 200,000-plus hectares can eventually accommodate from 1,000 to 2,000 horses. But like most zone scientists, her imagination often seemed to end at the international border. Belarus had an equivalent, if slightly smaller, exclusion zone and the border meant nothing to animals—like the bear that evidently wandered between the two countries in 2003—looking for new home ranges.

“The actual number may be smaller, because some young stallions may leave the zone in search of mares and may mate with domestic horses,” she explained.

A woman I know once took a morning stroll through the town of Chornobyl only to come across a lone Przewalski’s stallion grazing by the town’s vintage Lenin monument.

“But that’s a problem in all Przewalski’s introduction programs. In Mongolia, they capture the stallions and bring them back to the reserve. In Hungary, they’ve decided to limit population growth with contraceptives. As for what to do here …,” Tatiana sighed. “We don’t know.”

In a young forest of birches and pines inside the 10-kilometer zone, we spotted a pair of moose just a dozen yards or so away. Since it was still early in the season for the males to drop their antlers, the absence of antlers meant that they were female. One cow was resting on the ground and barely moved as we drove by, but her companion loped a few strides deeper into the woods before stopping and turning her head to watch us. I had never seen a moose so close—the bull I saw in Belarus was some distance away—and was stunned by their huge size.

Although Ukraine tried to maintain the barbed wire fence surrounding its portion of the 30-kilometer zone, it was more than 100 miles long and was down in many places. Belarus, meanwhile, didn’t even have a fence around its radioactive nature reserve. So there is little to prevent wild animals from passing freely in and out.

As with all zone animals that wander outside its borders, the Przewalski’s bachelors were at risk from poachers. “But these are very, very intelligent animals,” Tatiana said. “And when they perceive the difference between their quiet life here and the stresses outside the zone, they’ll quickly return.”

It was strange to think of a radioactive zone as a quiet sanctuary

for any animals, much less endangered and exotic species like Przewalski’s horses. Actually, however, the Przewalski’s horses’ life in the zone may not remain quiet if wolves figure out how to hunt them. “Some specialists told us that it can take wolves three years to learn to hunt new prey,” said Tatiana. “But five years have passed and the wolves evidently still haven’t learned to hunt the horses.” One reason may be that they have no need to. The zone is teeming with other meals for wolves.

“This is where we saw a pack of 12 wolves trying to chase down a lone stallion,” said Tatiana, as we drove through a fallow field succumbing to a future forest of pine saplings. “But he kicked one of the wolves in the teeth and got away easily.”

While watching a small group of roe deer canter along the forest in the distance, I thought I saw a large black object moving near some bushes about a hundred feet away.

“Isn’t that a moose?” I asked, pointing out my window. Everyone turned to look but didn’t see anything. “Just bushes,” Sasha started to say and I felt slightly foolish for imagining things until he exclaimed: “Boars!”

Woolly pigs started emerging from the brush and galloping parallel to our path, their dark, chunky bodies clearly visible against the snow, looking like miniature bison.

“I’ve never seen them so plainly before,” said Sasha, counting them quickly. “There must be 25 of them!” Feeling vindicated, I did my own rough estimate while realizing yet again why wild animal counts can only be approximate. They were moving too fast to count individually, so I estimated the space occupied by five boars and then tried to count how many of those spaces the herd occupied. “Thirty,” I said.

“Forty,” said Natalia as more wild pigs emerged. Chuckling over our escalating estimates, Tatiana said: “It’ll be 100 by the time we get back to Chornobyl.” But after the boars ran off, everyone agreed that it was an exceptionally large herd. “There were a lot of young ones, too,” Tatiana observed.

“Not a lot if you consider that each sow gives birth to six or so piglets,” said Sasha. “A lot of them die.”

“If all those piglets survived, we’d be drowning in boars,” said Natalia, adding: “So far, we’ve seen all of the zone’s ungulate species—except the horses.”

“Wolves like to hunt boars because each boar only protects itself,” Tatiana explained. “Horses protect themselves as well as the entire herd. Herd stallions are extraordinarily protective and strong animals.”

Once, when the scientists rode out to Vypad’s herd in a horse-drawn wagon, the stallion tried to attack the cart horse but didn’t actually go through with it only because there were people in the cart. “We try not to tame them, so that they don’t consider people too familiar.” said Tatiana. “Our horses almost never act aggressively towards people. But if we hadn’t been in the wagon, Vypad would have probably destroyed it and the horse.”

Once, a new stud stallion that Askania Nova brought from Slovakia attacked a horse carrying a rider and had to be beaten off with sticks and clubs. He was from a zoo and didn’t fear people at all.

A different complaint of some zoo breeders is a tendency to exclude aggressive Przewalski’s horses from breeding. “They think this reduces the horses’ chances for survival in the wild,” said Tatiana. “But at Askania Nova, we think that a very aggressive animal won’t survive in the wild. If a stallion keeps chasing and attacking wolves, at some point they’ll get him. The stallion has to be smart, and control the herd, getting it to a safe place instead of attacking predators—whether they are wolves or humans. He should attack the predator only if the predator actually attacks the herd.”

Soon we came to Cherevach, a former village on a deep-orange patch it shared with Chornobyl on the radioactive cesium maps. Sasha spotted fresh horse tracks and steaming manure and told Mykola to turn right and drive across a sandy field of rolling moraines formed by glaciers when Przewalski’s horses first roamed the region.

Five hours had passed. With no sign of the Przewalski’s, it was turning into a frustrating wild horse chase for the scientists—though I was having a fine time watching the other animals that crossed our path with exciting regularity. By lunchtime we had counted 4 red deer, 5 moose, 15 roe deer, and about 40 boars in a relatively small patch of what most of the world considered a dead zone.

I had planned to leave the zone by 2 p.m. to get back to Kiev before it was dark. Outside of cities and towns, Ukraine’s roads are unlit, and driving on them in a remote no-man’s-land was a little too adventurous for me, especially when it was freezing and the roads hadn’t been cleared of the day’s snow. But when we still hadn’t found the horses by my planned departure time, I decided to stay another night. I hadn’t jolted around in a lurching jeep for five hours just to give up so easily.

“If it was a hot summer day, the horses would just stand around in the same place,” said Natalia, scanning the horizon as we drove. “But in bad weather, they run around more.”

Our failure to see the horses reminded me of a conviction I entertained in third grade after a class trip to the New York Hall of Science. To this day, I remember the terrarium with a small sign reading: “The Impact of Radiation on Rats.” There was nothing in it except some plants, which convinced me that radiation had made the rats invisible! I’m not sure why I kept that stunning observation to myself. Maybe because I concluded that it was something everyone knew and I would look foolish commenting on the obvious. Certainly, none of my classmates seemed surprised by the invisible radioactive rats.

When we came to a wall of forest standing between us and what Sasha considered the right way to go, Mykola just gunned the motor and crashed right in, crushing saplings, small trees, bushes, and fallen logs and scaring off two roe deer that scampered into the forest. Then he descended onto a relatively smooth, sandy path that he drove down with the utter confidence of someone who knows that he won’t be running into any oncoming traffic, anywhere, anytime soon.

He stopped when Sasha spotted a fresh animal skeleton in a deep pile of snow-dusted grass on the side of the trail, but it was only a spine and ribcage. The head was missing, as were the legs, so there were no hoofs that would have helped identify it. From its size, the scientists guessed that it was a roe deer or a boar.

After driving for nearly eight hours over 60 miles of labyrinthine trails in Chernobyl back country, Sasha finally spotted the horses grazing on the edge of a forest in Korohod—the same village where he climbed the fire tower. But getting to them took half an hour, 20 minutes of which we spent crossing about 100 yards that had been so deeply gutted by boars that the jeep could move only a foot at a time, plunging into each crater and then emerging. Plunging and emerging. What I had thought were rough roads seemed like interstates in comparison. It was like riding a horse that was bucking and rearing in slow motion.

“Now, imagine if all the boars’ piglets actually survived,” Tatiana commented dryly after a Richter-scale plunge. “The entire zone would be like this.”

In the early postdisaster years, when radioactivity was on the surface, boars’ plowing was one of nature’s ways of fixing the stuff deeper into the soil. But now that 95 percent of the radionuclides are in the top two inches of the ground, the boars digging can expose them to dispersal by wind.

It was just five days short of being the shortest day of the year and the light was fading fast when we finally reached the horses. The snow had stopped, but the skies were gloomy.

“Won’t the sound of the jeep scare them away?” I asked when we stopped in view of them, but not too close, and piled out. It was windy and freezing outside, and Mykola stayed inside the jeep and kept the engine running.

“Nah,” said Sasha, opening the back of the jeep to take out a large burlap bag of oats. “For them, the sound of the engine is the sound of food.”

Indeed, the horses started approaching as soon as we stopped. Though they had spread out to graze, the horses herded together along the way and stopped about 15 yards from us. Sasha approached them slowly with the bag and dumped the grain into five small piles separated by a short distance.

“A quick way of determining the herd’s hierarchy is with supplemental feeding,” Tatiana explained. “You pour about two kilograms into each pile and separate the piles by a meter or two. They shouldn’t be so close together that one horse can take it all. But they should be close enough for the horses to have to fight for the food. As a rule, a horse that chases everyone away is higher in the hierarchy.”

I asked how the Chernobyl horse’s condition compares to the Przewalski’s horses in Askania Nova and was surprised to learn that they were actually better fed.

“Askania Nova is in the steppe. Except for springtime, the main fodder is dried grasses,” Natalia explained. “But green pastures are more nutritious, and in Polissia, which has a much wetter climate, there’s green fodder from spring to fall.”

Indeed, the horses had diversified their diet in the new surroundings. Aside from grass, they also browsed on birch and dog-rose twigs, even pine needles.

“We were shocked,” said Natalia. “Pine needles are considered poisonous for domestic horses.”

But the Przewalski’s horses were evidently doing fine eating pine, and radioactive pine at that.

The horses divided into groups of uneven and shifting size, giving the scientists an opportunity—fading quickly with the daylight—to count and identify the horses, figure out who had foaled, and record each youngster’s sex, color, and markings.

About as tall as large ponies but more robust, most of the Przewalski’s horses ranged in color from hay to chestnut, though they looked very much alike to me on such short acquaintance and lacked the range of colors and markings you see on domestic horses. All of them had black stockings that faded to stripes on the backs of their legs, creamy white muzzles with black nostrils, and stand-up manes like zebras, with no forelock.

They also displayed the distinctive Przewalski’s tail. On domestic horses, all of the tail hairs grow long and are the same color. But the Przewalski’s tail is two-toned and two-layered. The top, or dock, layer is short and the same color as the horse’s body, while the bottom layer is long and black. Some horses looked as though someone had teased their dock hairs into a beehive hairstyle.

The most distinctive of all the horses was Vypad, with his dark chocolate pelage and powerful build. Przewalski’s stallions’ necks grow in girth as they age, and 15-year-old Vypad’s was like a Clydesdale’s.

“In Askania, Vypad was in the bachelor group. Though he’s a fine specimen, we have to strictly limit breeding because we have no room for more horses,” Tatiana explained. “But when he turned 10, he started escaping from the bachelors’ enclosure, jumping over six-foot metal fences, to run into the steppe where the mares were. He had to be captured and brought back, but kept escaping nearly every day. So, when the time came to choose horses to send here to Chernobyl, we decided that a stallion with that kind of character was an excellent choice to lead a herd. And we were right.”

Vypad was munching from a grain pile on the edge of the herd, together with a pretty hay-colored mare with a creamy belly, blond highlights in her mane, and eyes ringed with gold. She was the lightest horse in the herd and almost as distinctive as Vypad. The scientists identified her officially as No. 2366—her number in the international Przewalski’s studbook—and nicknamed her Vyzitka, or “visiting card.” I thought of her as Blondie (Plate 5).

The studbook was created in 1959 by the Prague Zoo, when the number of Przewalski’s horses in captivity was low, the numbers in the wild were still lower, and the dangers of inbreeding were high. Today, it is a unique record of one of the most intensely managed exotic species in captivity.

“That’s the lowest-ranking mare,” said Tatiana, pointing to Blondie. “She’s staying close to Vypad because none of the other mares dare to pick on her while he’s nearby. If one of them tried, he’d wallop her. He doesn’t tolerate aggression in his presence.”

But there was aggression going on in places where he wasn’t looking. While a few foals nursed and other horses engaged in placid mutual grooming, the rest milled around, bumping about their hierarchy in sudden eruptions of spins and kicks, flattened ears, and snapping mouths.

Przewalski’s herds behave in much the same way as domestic horse herds, such as American mustangs, when there is little human interference. Yet because the existing Przewalski’s population has been kept in captivity for up to 12 generations, it is difficult to know if the similarities exist because Przewalski’s and domestic horses have a close evolutionary relationship or because both have lived in captivity.

Tatiana explained that there is no way to diagram the herd’s social structure in such a short time. It required many hours of observation, especially since the hierarchy wasn’t linear but resembled a network.

“If one horse submits to another’s warning once, it doesn’t mean much. But if it submits five times, you can make conclusions about ranking,” she said. “Sometimes submitting is as subtle as just stepping aside when a higher-ranking horse passes.”

With the birth of young colts and fillies, Blondie finally had even lower-ranking individuals to pick on and did so with great evident enjoyment, although her low ranking with the adult mares was unchanged.

Like all of Askania Nova’s Przewalski’s horses, the Chernobyl herds are descended from Orlitza III, the last of the species caught in the wild. Brought to Askania Nova in 1957, Orlitza III became enormously important in the Przewalski’s captive breeding programs. After World War II, when many of the horses died, the 31 horses that survived were all descendants of 12 founders, one of whom was the domestic mare foster mother. Rates of inbreeding were so high as to lower fitness, fertil-

ity, and life span. By injecting desperately needed new blood into the Przewalski’s pedigree, Orlitza III did much to improve the captive population, including its fertility. Orlitza’s descendants produced more foals than other Przewalski’s lines. Perhaps Vypad inherited his strong need to breed from his great-great grand dam.

Next to Vypad and Blondie, a lone mare was trying to keep a pile all to herself. If any other horse tried to approach it, she’d flatten her ears and snap, or whirl and threaten to kick. I didn’t see her actually connect with any of her would-be dining partners, but they got the message and generally wandered over to Vypad’s end.

“She must be pretty high in the hierarchy,” I observed.

“Actually, lower-ranked horses can also be aggressive,” said Tatiana. “You don’t just look at whether the horse displays aggression, but at the result. If one horse threatens to bite another to move it away from the grain pile, but the other horse doesn’t move, the first one is probably lower ranked.”

Tatiana returned her attention to identifying the horses in the remaining minutes before darkness fell. “If only we had found them half an hour earlier,” she lamented.

Once it was too dark to identify the horses, I followed Tatiana and Natalia to collect manure samples so that they could check the horse’s internal parasites.

“Stay close to us so that the horses don’t think we’re circling them,” said Natalia. “They’ll consider that threatening.”

As soon as we started approaching, the horses herded together and moved away, but they were clearly reluctant to leave the remaining oats and didn’t go very far.

Blanketed with dried grasses and light snow, the ground was rutted by boars, and the light was fading very fast, making it hard for me to distinguish dung from dirt. Not being of much use, I trudged back to the jeep to sit in a relatively warm place for a few minutes. It was bitterly cold. But the hardy Przewalski’s horses seemed untroubled by the temperature. Horses handle cold weather well when it’s dry, but they don’t much like rain or wind.

When I could feel my fingertips again, the horses had returned to the grain piles and the scientists were returning to the car, their feet loudly crunching the dried grass. Sasha was trying to shush them so that he could better hear a distant barking.

“Lynx,” said Sasha. “Maybe red deer.”

“It’s too loud to be a deer,” said Mykola.

When the barking stopped, Tatiana chided me: “Mary, why did you leave? Didn’t you see what happened? They came to us and stood just a few feet away.”

From her excitement it was clear I had missed something extraordinary. It was also clear that these two women cared for the horses too much to intentionally do anything to harm them. It was hard not to share their optimism about the Przewalski’s horses’ future in the zone.

“It’s when we crouched to collect the samples,” Natalia explained. “We seemed smaller to them—less threatening—and they also probably thought we were bringing more oats.”

It was the first time that the scientists had been so close to the horses.

“They’re very curious,” said Tatiana after we had piled back into the jeep and started our return journey to Chornobyl. “If you want to photograph them, walk towards them swiftly and then suddenly crouch or sit down. When you seem that small, they’ll come over to see what’s going on. But that’s only with Vypad’s herd. Since we work with them so closely, they aren’t that scared of us.”

“If you tried that with Volny’s herd, they’d hightail it out of there,” Natalia added. Volny was much shyer than Vypad.

The scientists counted 25 horses in Vypad’s family: 8 adult mares that had come from Askania Nova together with 7 foals and 9 juveniles born in the wild. The stallion was a fertile fellow and had had a prolific year. But they failed to identify all of the foals because larger horses often blocked their view. Definitely identifying the juveniles was also tricky since some looked very much alike and had to be observed at different angles.

“It would be easy if they just stood still,” said Natalia. “But they don’t.”

“For example, we think that the very aggressive mare was the first Chernobyl foal born in 1999,” Tatiana added. “But we’re not completely sure.”

That would make the young mare, nicknamed Pripyat, more than four years old and well past the age when stallions chase their daughters out of the herd. To prevent inbreeding, juveniles are expelled when they are between two and three years old. That year,Vypad had already expelled some of his older offspring, and the scientists were eagerly

hoping that some bachelor stallions would pick up the young mares to form new harem groups and increase the Chernobyl Przewalski’s horses’ genetic diversity.

If the mare was Pripyat, perhaps Vypad was letting her stay because he wasn’t her father. Her mother got pregnant in Askania Nova, where Vypad wasn’t allowed to breed. Actually, some Przewalski’s stallions have been known to kill foals when they take over a harem. But for all his fearsome appearance and reputation, Vypad was a gentle daddy. He was rarely aggressive towards the foals, and in the winter, when the horses dig pits in the snow to reach the grass beneath, he shared his pit with the foals. No mare in the herd has been seen sharing her snow pit with a foal that isn’t her own. Of course, each mare has but one foal at a time. Vypad had to take care of all his offspring.

It was still dark outside when the jeep picked me up at the Chornobyl hotel at seven the next morning. Eager to continue their study of Vypad’s herd, the scientists wanted to take full advantage of the short winter day and, hopefully, catch the horses at the same place we had seen them the previous evening, before they galloped off to a different part of their enormous range. In fact they were so eager, they kept dozing off in the back seat because, Tatiana later confessed, they had been so worried their alarm wouldn’t go off in the morning, they couldn’t sleep half the night.

The jeep’s headlights illuminated a path on the snow-packed roads and trails as we drove 40 minutes through the darkness to the field in Korohod, only to find that the horses had already left. The jeep stank of exhaust even worse than I remembered, so it was a relief to get out while Sasha and the scientists examined the hoof prints in the snow to see which way the herd had gone. The rising sun was merely a pink smear above the tree line when we set off in the direction of the 10-kilometer zone, back on one of the paths we had taken the previous day. I recognized it only because of an empty sardine can someone had tossed aside in the sand.

After another 40 minutes of bumping along rough trails and then crossing another cratered field dug by boars, we found the horses near the border of the 10-kilometer zone and in view of the abandoned Soviet radar station nicknamed Chernobyl-2. It would be redundant

to say that the station had been secret in Soviet times. Nearly anything that wasn’t in plain sight was a Soviet secret, and to make sure that too many people didn’t see what was in plain sight, permits were required to enter entire cities and regions. Foreigners were banned altogether from many places.

The sun had risen over overcast skies when we stopped, but the freezing, windy weather persisted. Once again, Sasha poured grain into separate piles and the horses approached, standing less than 30 feet away from us as they divided into groups around the grain piles and repeated their hierarchy rituals. The aggressive mare of yesterday was evidently on better behavior, though, making her harder to identify.

The scientists set to work immediately, examining the horses, making notes, and holding esoteric exchanges along the lines of:

“Foal nursing number 161. Male. Dark spot on nose.”

“That’s not 161. She has a star. It’s 159.”

“Damn! 163 just blocked my view.”

Though all the horses that came from the nature reserve have international studbook numbers, the scientists were using Askania Nova’s internal nomenclature that they use to count only their own animals. They were recording the foals’ markings for future identification and trying to figure out which foals belonged to which dams. One way to be reasonably certain was to see which mare was nursing them. Even that wasn’t a sure thing, though. In zoos, Przewalski’s dams have been known to nurse their daughters’ foals, and daughters have been observed nursing their mothers’ foals. But since sexually mature offspring are expelled under natural conditions, that shouldn’t happen in the wild.

While the horses engaged in their hierarchical rituals of snapping, spinning, and kicking over access to the tasty treats, one yearling colt evidently decided that fighting over swiftly dwindling piles wasn’t worth the trouble when he caught a whiff of the large sack of remaining oats that Sasha had placed behind the jeep.

“He’s the tamest,” said Natalia as the colt faced the jeep from a distance of about 20 feet and stretched his neck to smell the oats. “He’s the least afraid of people.”

A few other horses gathered near him as he approached the sack incrementally. Step, stop. Step, stop. If another horse got too close, he

whirled and kicked, but since he was clearly the only one among them who was brave enough to lead the way to the sack, the rest followed meekly enough and kept a respectful distance. By the time he was a nose away from the jeep, about a quarter of the herd was right behind him, including Vypad who didn’t seem to be pulling rank in any way. But when the colt finally touched his nose to the sack, his own audacity—or our proximity just a few yards away—proved to be too much and he spun around, prompting all the horses to gallop to a safer distance.

The horses had finished eating the oats by then and Sasha wanted to pour them more, but Tatiana stopped him.

“They’re packed too close together by the piles and we can’t get a good look at them,” she explained. “If there’s no more food here, they’ll start grazing and spread out.”

Instead, the horses just stood and watched us—and the sack—expectantly. Mykola, the driver, sat on it to keep the horses from approaching it again, but this didn’t keep them from hoping, even after Mykola put the sack back in the jeep and turned on the engine and clouds of exhaust fumes floated over the herd.

“So long as they see the jeep, they don’t lose hope,” said Natalia.

Blondie stood by herself, a short distance from the rest of the herd, perhaps because higher-ranking mares had surrounded Vypad. He gently nuzzled a golden mare’s withers and rubbed his face against hers. It seemed like a tender display except it was actually a sign of dominance. The dominant animal rubs but does not allow itself to be rubbed.

But the display angered the alpha mare, who charged up to the pair, snapped to chase her rival away and then opened her mouth to stroke the stallion all over his head. Thus assured of his attention, she ambled away.

Though Vypad was the highest-ranking horse in his herd, the stallion is not always the alpha animal in harem groups, especially in captivity. If a young stallion is joined to an established group of mares as a stud, high-ranking (and generally older) mares simply won’t breed with him. A stallion must outrank a mare before he can mate with her.

In the wild, though, new herds are formed when bachelor stallions fight for access to young mares that have been expelled from their family harems. The winning stallions are almost always older and more experienced than their rivals and more dominant than their first mares, so that the stallion is top ranking. But when a strong and experienced

bachelor eventually wins Vypad’s herd—and that day will inevitably come—it is unlikely that he’ll be able to dominate, or breed with, the older mares.

After about an hour, the horses decided that no more food was forthcoming and they started slowly moving a short distance away from us to graze. Vypad followed in the rear, stopping occasionally to turn around and look at the jeep.

When the horses spread out, Sasha and the scientists approached them hoping to finally get a good look at the foals, while I climbed into the jeep to warm up and make some notes. The smell of exhaust inside was suffocating, though. After a few moments, I climbed back out into the cold, upwind from the exhaust belching from the jeep, and walked slowly towards the horses, trying to imagine myself an Ice Age huntress scouting a horse herd on the periglacial steppe that covered Polissia when modern humans arrived in the region around 25,000 to 30,000 years ago.

After a while, the horses had grazed their way some distance from the jeep, so Mykola started the engine to drive closer. But for the horses, the engine meant “grain!” and they quickly herded together, prompting annoyed grumbling from the scientists when they returned to the car, with the herd following close behind.

For a few moments, horses and humans stood quietly and watched each other, filled with hopes of getting something. The horses’ hopes were simple: food. But what were we humans hoping for? I couldn’t speak for anyone, but I was hoping for a few more moments of communion with animals that seemed to symbolize our enormously complex and complicated relationship with our planet. Humans brought Przewalski’s horses to the brink of extinction and then gave the species a chance for a new future in the wild. How ironic it was that one of the few places on Earth where they can live in the wild, free from human threats, is a radioactive land that threatens humans more than it seems to threaten them.